1. Field of the Invention
This invention relates generally to rotating magnetic storage devices, and more particularly to read channel control devices that can generate control signals for controlling read/write operations in the rotating magnetic storage devices.
2. Description of the Related Art
Modem computer systems typically include one or more hard disk drives in which a large amount of data, including operating system files, application programs, and other files can be stored. The hard drives typically store information in one or more hard disks using magnetic technology. Each hard disk is configured in concentric tracks, each of which is divided into sectors.
For data storage and access, conventional hard drives typically employ one or more read/write heads to write or read data to and from a specified track in the disk. A track in a hard disk typically includes servo fields and data fields. The servo fields store embedded servo data patterns used to properly position the read/write heads over the tracks while the data fields store end user data.
Conventional hard drives generally employ linear or rotary head positioning mechanisms to properly position and maintain the read/write heads over the desired tracks for reading or writing data. The head positioning mechanisms typically use a set of signals for controlling read/write channel control. For example, a read gate signal is used to recover encoded user data from data fields while a write gate signal is used in writing user data to data fields. In addition, a servo gate signal is used to recover encoded servo data from servo fields.
From these signals, conventional head positioning mechanisms typically generate derivative signals to perform various control functions in a read channel device. For example, one derivative signal LOWZ is generated to set a first stage read amplifier to low impedance to remove stored voltage from an earlier write operation. Another derivative signal FACQ sets the first stage read amplifier into xe2x80x9cfast attackxe2x80x9d mode to quickly adjust to the input signal strength, i.e., amplitude. A control signal version of the read gate signal sets the first stage read amplifier to xe2x80x9cnormal trackingxe2x80x9d mode to follow and compensate for modulation in the input signal strength. In addition, the control signal version of the read gate signal modifies the data recovery channel bandwidth to optimize signal to noise ratio for the input signal frequency. A data recovery device in the hard drive then uses these signals to control the read/write operations of read/write heads.
Unfortunately, however, these channel control functions require costly external circuitry to extend read gate, write gate, or servo gate signals. In particular, producing pulse of programmable duration at the leading or trailing edges of read gate, write gate, or servo gate signals requires expensive external circuitry. In addition, the signal requirements for data recovery devices in the industry vary substantially. For example, each data recovery device may use different signals with varying polarity and timing requirements. Hence, the channel control functions typically needs to be customized to fit different data recovery devices. As can be appreciated, such customization can be costly to implement.
Thus, what is needed is a programmable channel read channel control device that is programmable for use with a variety of different data recovery devices without the cost associated with conventional devices.
Broadly speaking, the present invention fills these needs by providing a programmable generic read channel control device and circuitry. It should be appreciated that the present invention can be implemented in numerous ways, including as a process, an apparatus, a system, computer readable media, or a device. Several inventive embodiments of the present invention are described below.
In one embodiment, the present invention provides a programmable generic read channel control device for generating an output signal to control read/write operations. The programmable generic read channel control device includes a set of extension timers, a set of configuration registers, a set of AND gates, and an OR gate. The extension timers are programmed to generate a set of pulses of programmable width in response to a read gate and write gate signal. Each of the pulses may include a leading edge pulse and a trailing edge pulse. The configuration registers store a set of configuration data for the pulses with each configuration register storing one configuration data for either a leading edge or a trailing edge pulse of one of the pulses. The configuration data indicates whether the associated pulse is enabled. The AND gates are arranged to receive the pulses of programmable width with each AND gate receiving either a leading edge or a trailing edge of one of the pulses as a first input. Each AND gate also receiving a configuration data as a second input that allows the first input to be transmitted as an output signal when the configuration data at the second input is enabled. The OR gate is arranged to combine the output signals from the set of AND gates to generate the output signal such that the output signal is generated from only the leading or trailing edges of the pulses from the AND gates receiving the enable signals. The set of extension timers includes a short write gate extension timer configured to generate a write gate short leading edge pulse and a write gate short trailing edge pulse defining a write gate short pulse width. In addition, a flip-flop may be provided to receive a set of first control signals for setting and resetting the output signal of the OR gate.
In another embodiment, the present invention provides a programmable generic read channel control circuitry for generating an output signal to control read/write operations. The programmable generic read channel control circuitry includes a set of extension timers, a set of AND gates, and an OR gate. A first extension timer is capable of storing a first time value for generating a first pulse width in response to a read gate signal. A second extension timer is capable of storing a second time value for generating a second pulse width in response to the read gate signal. A third extension timer is capable of storing a third time value for generating a third pulse of programmable width in response to a write gate signal. A short write gate extension timer is capable of storing a fourth time value for generating a write gate short leading edge pulse and a write gate short trailing edge pulse defining a fourth pulse of programmable width in response to the write gate signal. Each of the pulse width is defined by a leading edge and a trailing edge. The AND gates are arranged to receive the pulses of programmable width, with each AND gate receiving either a leading edge or a trailing edge of one of the pulses as a first input. Each AND gate also arranged to receive an enable signal as a second input that allows the first input to be transmitted as an output signal when the enable signal at the second input is active. The OR gate is arranged to combine the output signals from the set of AND gates to generate the output signal such that the output signal is generated from only the leading or trailing edges of the pulses from the AND gates receiving the enable signals.
Advantageously, the programmable generic read channel control logic device and circuitry of the present invention allows any input signals to be combined in any suitable manner to meet the requirements of wide variety of read/write channel devices. This eliminates the need for costly external circuitry and produces a single device that is capable of controlling a variety of read/write channel devices that have different signal requirements. Thus, the programmable read channel control logic device provides significant savings in design cost. Other aspects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.